Work out reaction enthalpy instantly with clear inputs, formula shown and shareable results.
Standard reaction enthalpy is the total formation enthalpy of the products minus that of the reactants, each weighted by its coefficient. A negative result means the products sit lower in energy and heat leaves the system. Scaling by the moles actually run converts the per-mole figure into the energy a given batch releases or requires.
Hess summation
dH(rxn) = sum dHf(products) - sum dHf(reactants)
Batch energy
energy = dH(rxn) x moles of reaction
No. An element in its standard state has dHf = 0 by definition, so it contributes nothing to either sum.
Enthalpy is measured from the system's point of view. Losing enthalpy to the surroundings makes the change negative and the flask warm.